Determinants of lung volume in spontaneously breathing preterm infants.

Abstract

To study the effects of apneic pauses, sighs, and breathing patterns on functional residual capacity (FRC), we measured FRC repeatedly in 48 healthy preterm infants (weight at study 2,042 +/- 316 g [mean +/- SD], postconceptional age 36.6 +/- 2.0 wk), during unsedated sleep using a modified heliox/nitrogen washout technique. Breathing movements and pulse oximeter saturation (SpO2) were recorded throughout and recordings analyzed for the presence of regular and nonregular breathing pattern, apneic pauses, sighs, and desaturations (SpO2 < 90%) during the last 2 min prior to each FRC measurement. FRC was lower during nonregular than during regular breathing pattern (23.3 +/- 7.2 ml/kg versus 26.9 +/- 7.8 ml/kg, p < 0.02); however, this apparent effect of breathing pattern disappeared after controlling the data for apneic pauses. Apneic pauses resulted in a significant decrease in FRC: mean FRC was 20.0 +/- 6.8 ml/kg if measured within 2 min of an apneic pause, 26.0 +/- 6.9 ml/kg if measured after a sigh (p < 0.001), and 24.0 +/- 7.7 ml/kg if there had been neither a sigh nor an apneic pause (p < 0.05). The interval between the apneic pause and the FRC measurement had no effect on FRC. There was an inverse correlation between FRC and the speed with which SpO2 fell during desaturation (r = -O.5, p < 0.03). Apneic pauses resulted in a persistent reduction in FRC in these preterm infants. Sighs appeared to restore FRC. The significant relationship between FRC and the speed of desaturation found in this study underscores the importance of endogenous or exogenous strategies that help to increase FRC, such as sighs or the application of continuous positive airway pressure, for the stability of oxygenation in preterm infants who have difficulty maintaining their oxygenation.

Periodic Breathing and Oxygen Saturation in Preterm Infants at Discharge

“…Poets et al 10 showed that lung volumes are low during PB in spontaneously breathing preterm infants. These findings of decreased mixed venous pO 2 and lung volumes may explain the relationship between PB and episodes of oxygen desaturation.…”

Mechanical Ventilation of the Premature Neonate

“…23 It has been speculated that PSV may better enable a ventilated neonate to establish a breathing pattern that includes sighs. 24 PSV may be particularly useful in patients who are difficult to manage with a fixed inspiratory time and respiratory rate (eg, PC-CMV).…”

Relationship between oxygen saturation and the mode of oxygen delivery used in newborn resuscitation

“…14,17,22 Others have demonstrated that a properly inflated lung is important in achieving and maintaining proper oxygenation and that infants with inadequate FRC are more prone to desaturation events. [10][11][12][13] Deckardt et al continuously measured SpO 2 of newborns and delivered continuous positive airway pressure to those who failed to achieve an SpO 2 of 80% by 5 min of age. 4 They found that the use of continuous positive airway pressure improved oxygenation.…”

“…5,9 For infants requiring resuscitation, the mode of oxygen (O 2 ) delivery may be an important factor in affecting oxygenation. [10][11][12][13] Oxygenation is promoted by providing supplemental O 2 and/or establishing functional residual capacity (FRC) using positive pressure. Continuous positive airway pressure is effective at establishing FRC in the newborn and reducing ventilationperfusion mismatch through recruiting collapsed alveoli and stabilizing alveoli that are already patent, thereby improving oxygenation.…”